Tiled solar cell laser process

ABSTRACT

In an example, the present invention provides a method of separating a photovoltaic strip from a solar cell. The method includes providing a solar cell, placing the front side of the solar cell on a platen such that the backside is facing a laser source, initiating a laser source to output a laser beam having a wavelength from 200 to 600 nanometers and a spot size of 18 to 30 microns, subjecting a portion of the backside to the laser beam at a power level ranging from about 20 Watts to about 35 Watts to cause an ablation to form a scribe region having a depth, width, and a length, the depth being from 40% to 60% of a thickness of the solar cell, the width being between 16 and 35 microns to create a plurality of scribe regions spatially disposed on the backside of the solar cell.

This application is a continuation of U.S. application Ser. No.16/691,408 filed Nov. 21, 2019, which is a continuation of U.S.application Ser. No. 16/418,859 filed May 21, 2019, now issued as U.S.Pat. No. 10,522,707 on Dec. 31, 2019, which is a continuation of U.S.application Ser. No. 15/622,000, filed Jun. 13, 2017, now issued as U.S.Pat. No. 10,347,788 on Jul. 9, 2019, which is a non-provisional of U.S.Provisional Application No. 62/349,547, filed Jun. 13, 2016, and thisapplication also claims priority to U.S. patent application Ser. No.14/609,307, filed Jan. 29, 2015, which is incorporated by referenceherein for all purposes.

BACKGROUND OF THE INVENTION

The present invention is directed to photovoltaic systems andmanufacturing processes and apparatuses thereof.

As the population of the world has increased, industrial expansion hasled to a corresponding increased consumption of energy. Energy oftencomes from fossil fuels, including coal and oil, hydroelectric plants,nuclear sources, and others. As merely an example, the InternationalEnergy Agency projects further increases in oil consumption, withdeveloping nations such as China and India accounting for most of theincrease. Almost every element of our daily lives depends, in part, onoil, which is becoming increasingly scarce. As time further progresses,an era of “cheap” and plentiful oil is coming to an end. Accordingly,other and alternative sources of energy have been developed.

In addition to oil, we have also relied upon other very useful sourcesof energy such as hydroelectric, nuclear, and the like to provide ourelectricity needs. As an example, most of our conventional electricityrequirements for home and business use comes from turbines run on coalor other forms of fossil fuel, nuclear power generation plants, andhydroelectric plants, as well as other forms of renewable energy. Oftentimes, home and business use of electrical power has been stable andwidespread.

Most importantly, much if not all of the useful energy found on theEarth comes from our sun. Generally, plant life on the Earth achieveslife using photosynthesis processes from sunlight. Fossil fuels such asoil were also developed from biological materials derived from energyassociated with the sun. For life on the planet Earth, the sun has beenour most important energy source and fuel for modern day solar energy.

Solar energy possesses many desirable characteristics; it is renewable,clean, abundant, and often widespread. Certain technologies developedoften capture solar energy, concentrate it, store it, and convert itinto other useful forms of energy.

Solar panels have been developed to convert sunlight into energy. Forexample, solar thermal panels are used to convert electromagneticradiation from the sun into thermal energy for heating homes, runningcertain industrial processes, or driving high-grade turbines to generateelectricity. As another example, solar photovoltaic panels are used toconvert sunlight directly into electricity for a variety ofapplications. Solar panels are generally composed of an array of solarcells, which are interconnected to each other. The cells are oftenarranged in series and/or parallel groups of cells in series.Accordingly, solar panels have great potential to benefit our nation,security, and human users. They can even diversify our energyrequirements and reduce the world's dependence on oil and otherpotentially detrimental sources of energy.

Although solar panels have been used successfully for certainapplications, there are still certain limitations. Solar cells are oftencostly. Depending upon the geographic region, there are often financialsubsidies from governmental entities for purchasing solar panels, whichoften cannot compete with the direct purchase of electricity from publicpower companies. Additionally, the panels are often composed of costlyphotovoltaic silicon bearing wafer materials, which are often difficultto manufacture efficiently on a large scale, and sources can be limited.

Solar cells are manufactured in a set of predetermined sizes. Forexample, cells are typically produced to have a width and length ofapproximately 156 mm. Current, voltage and resistance for such cells arelargely related to the material and size characteristics of the cells.For example, cell current is directly proportional to cell area.Therefore, standard size solar cells tend to have very similarcharacteristics, which limits the ability of manufacturers to optimizecharacteristics of modules that employ a plurality of cells.Accordingly, some manufacturers cut standard sized cells into smallerparts, which may be referred to as strips, to affect the characteristicsof the photovoltaic materials.

Conventionally, solar cells are mechanically cut with a saw. However,this technique has numerous disadvantages. The saw blades are veryexpensive, and must be replaced regularly. Saw blades wear quickly, sothe quality of cuts progressively degrades after the first cut. Sawcutting processes generate a substantial amount of heat at the cuttingsurface, which can damage a cell. The combination of particulate andforce from the cutter can cause particulate to be embedded in the cells,leading to degraded performance. In addition, water flushing to removeheat and particulate in a mechanical cutting process can damage cells.

Therefore, it is desirable to have novel system and method formanufacturing solar panels.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to photovoltaic systems andmanufacturing processes and apparatuses thereof.

In an example, a method includes providing a solar cell comprisingeither a single crystalline silicon material or a polycrystalline solarcell, the solar cell having a backside and a front side and a thickness,the backside having a metal material, placing the front side of thesolar cell on a platen such that the backside is facing a laser source,initiating a laser source to output a laser beam having a wavelengthfrom 200 to 600 nanometers and a spot size of 18 to 30 microns,subjecting a portion of the backside to the laser beam at a power levelranging from about 20 Watts to about 35 Watts to cause an ablation toform a scribe region having a depth, width, and a length, the depthbeing from 40% to 60% of a thickness of the solar cell, the width beingbetween 16 and 35 microns, and the length being equivalent to a lengthof the solar cell, and repeating the step of subjecting to create aplurality of scribe regions spatially disposed on the backside of thesolar cell.

In an embodiment, the method includes moving the laser beam at a rate of4800 to 5000 mm per second. The method may include subjecting the cellto the laser at least twice along the scribe region. In an example, thecell is subjected to the laser in 10 to 25 passes.

In an example, the scribe region is shaped as a notch as viewed along anend of the scribe region.

In an example, the method further includes detecting a thickness of thesolar cell and setting at least one of speed of a movement of the laserbeam or number of passes based upon the thickness of the thickness ofthe solar cell.

In an example, the detecting includes applying a red laser to a surfacesolar cell to identify a height of the thickness of material.

In an example, the method includes adjusting a number of passes for thescribe region to accommodate a thickness variation of the thickness ofthe solar cell.

In an example, the detecting occurs using a laser having a differentcolor than the laser beam from the laser source. The separating mayoccur within a time frame of 1 second to about 6 seconds to provide theplurality of scribe regions.

In an example, the laser beam has a wavelength in the green spectrum.

In an example, the method includes delivering a jet of fluid within avicinity of the ablation to carry away particulate material, andcapturing the particulate material using a vacuum.

In an example, the method includes subjecting a fluid, using a laminarflow, within a vicinity of the ablation to carry away particulatematerial, and capturing the particulate material using a vacuum.

In an example, the method includes maintaining the cell in asubstantially flat position using a vacuum chuck. In an example, thescribe region is a straight line +/−10 microns.

In an example, the method includes scribing a unique identifier on eachof the strips. In an example, the solar cell is from 170 to 220 micronsthick.

In an example, the laser beam is directed at a backside surface of thesolar cell that includes a thickness of aluminum.

In an example, the method includes singulating a strip from the solarcell by applying mechanical stress to a region of the solar celladjacent to scribe region.

In an example, the scribe region is located, at least in part, betweentwo adjacent bus bars of the solar cell.

In an example, the method includes providing a solar cell comprisingeither a single crystalline silicon material or a polycrystalline solarmaterial, the solar cell having a backside and a front side and athickness, the backside having a metal material, and placing the frontside of the solar cell on a platen such that the backside is facing alaser source. The method includes initiating a laser source to output alaser beam having a 532 nm wavelength and a spot size of 18 to 30microns and subjecting a portion of the backside to the laser beam in areduced power level ranging from about 20 Watts to about 35 Watts tocause an ablation to form a scribe region having a depth, width, and alength, the depth being about ½ of the thickness of the solar cell, thewidth being about ¼ of the depth, and the length being equivalent to alength of the solar cell. The method includes detecting a thickness ofthe solar cell and adjusting a speed of a movement of the laser beambased upon a thickness variation of the thickness of the solar cell. Themethod includes repeating the step of subjecting to create a pluralityof scribe regions spatially disposed on the backside of the solarmodule.

In an example, the method includes moving the laser beam at a rate of4800 to 5000 mm per second. In an example, the method includessubjecting at least twice along the scribe region. In an example, thescribe region is shaped as a notch as viewed along an end of the scriberegion. In an example, the detecting comprises applying a red laser to asurface solar cell to identify a height of the thickness of material. Inan example, the adjusting comprises adjusting a number of passes for thescribe region to accommodate a thickness variation of the thickness ofthe solar cell. In an example, the detecting occurs using a laser havinga different color than the laser beam from the laser source. In anexample, the method of separating occurs within a time frame of 1 secondto about 6 seconds to provide the plurality of scribe regions. In anexample, the method further includes maintaining vacuum near a vicinityof the solar cell during the subjecting. In an example, the methodincludes subjecting a jet of fluid within a vicinity of the ablation tocarry away particulate material, and capturing the particulate materialusing a vacuum. In an example, the method includes subjecting a fluid,using a laminar flow, within a vicinity of the ablation to carry awayparticulate material, and capturing the particulate material using avacuum. In an example, the method includes retaining the solar cell on avacuum chuck to maintain the cell in a substantially flat position. Inan example, the scribe region is a straight line +/−10 microns. In anexample, the method includes scribing a unique identifier on each of thestrips.

In an example, a solar module apparatus is provided. The apparatus has aplurality of strings, each of the plurality of strings being configuredin a parallel electrical arrangement with each other and a plurality ofphotovoltaic strips forming each of the plurality of photovoltaicstrings. The apparatus has a first end termination configured along afirst end of each of the plurality of strings and a second endtermination configured along a second end of each of the plurality ofstrings. The module has an equivalent diode device configured betweenthe first end termination and the second end termination such that oneof the plurality of photovoltaic strips associated with one of theplurality of strings when shaded causes the plurality of strips (“ShadedStrips”) associated with the one of the strings to cease generatingelectrical current from application of electromagnetic radiation, whilea remaining plurality of strips, associated with the remaining pluralityof strings, each of which generates a current that is substantiallyequivalent as an electrical current while the Shaded Strips are notshaded, and the equivalent diode device between the first terminal andthe second terminal for the plurality of strips is configured to turn-onto by-pass electrical current through the equivalent diode device suchthat the electrical current that was by-passed traverses the equivalentdiode device coupled to the plurality of strips that are configuredparallel to each other.

Many benefits can be achieved by ways of the present invention. As anexample, the present module can be made using conventional process andmaterials. Additionally, the present module is more efficient thanconventional module designs. Furthermore, the present module, andrelated techniques provides for a more efficient module usage usingby-pass diodes configured with multiple zones of solar cells. Dependingupon the example, there are other benefits as well.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a solar cell article according toan example of the present;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a first side view thereof;

FIG. 7 is a second side view thereof;

FIGS. 8-12 are illustrations of an edge photovoltaic strip according toan example of the present invention;

FIGS. 13-17 are illustrations of a center photovoltaic strip accordingto an example of the present invention;

FIGS. 18-20 illustrate a photovoltaic string according to an example ofthe present invention;

FIGS. 21-25 illustrate a solar module according to an example of thepresent invention;

FIG. 26 is a front view of a solar cell in an example of the presentinvention;

FIG. 27 is a side view of the solar cell, including bus bars, in anexample of the present invention;

FIG. 28 is an expanded view of a bus bar in an example of the presentinvention;

FIGS. 29-33 illustrate a solar cell under a cut and separation processaccording to an example of the present invention;

FIG. 34 is a top view of a photovoltaic string according to an exampleof the present invention;

FIG. 35 is a side view of the photovoltaic string according to anexample of the present invention;

FIG. 36 is a simplified diagram of a simplified system diagram accordingto an example of the present invention;

FIG. 37 illustrates a process for scribing and singulating a solar cellusing laser energy according to an example of the present invention;

FIG. 38 illustrates a laser cutting system according to an example ofthe present invention;

FIG. 39 illustrates kerfs in a solar cell according to an example of thepresent invention;

FIG. 40 a laser etched identifier according to an example of the presentinvention;

FIG. 41 illustrates experimental results of various laser power levels;and

FIG. 42 illustrates experimental results for relationships between cellvelocity and kerf depth.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to photovoltaic systems andmanufacturing processes and apparatus thereof. There are otherembodiments as well.

Embodiments of the present invention provide system and methods formanufacturing high density solar panels. Embodiments of the presentinvention use overlapped or tiled photovoltaic strip elements toincrease the amount of photovoltaic material, thereby increasing anamount of power, while reducing an amount of series resistance losses inthe solar panel. It is noted that specific embodiments are shown forillustrative purposes, and represent examples. One skilled in the artwould recognize other variations, modifications, and alternatives.

Although orientation is not a part of the invention, it is convenient torecognize that a solar module has a side that faces the sun when themodule is in use, and an opposite side that faces away from the sun.Although, the module can exist in any orientation, it is convenient torefer to an orientation where “upper” or “top” refer to the sun-facingside and “lower” or “bottom” refer to the opposite side. Thus an elementthat is said to overlie another element will be closer to the “upper”side than the element it overlies.

While the above is a complete description of specific embodiments of theinvention, the above description should not be taken as limiting thescope of the invention as defined by the claims.

The present disclosure describes a process, system and product for solarcells cut using a laser scribing process. A laser scribing process hasnumerous advantages over a conventional mechanical sawing process. Lasercomponents have extended life cycles, so maintenance and replacementcosts are very low compared to mechanical sawing, which requires regularreplacement of high precision saw blades. A laser scribing process iscleaner since mechanical sawing requires a substantial volume of liquidto flush the cutting area. Damage to cells is reduced by a laserprocess, increasing throughput and reducing costs.

FIG. 1 is a front perspective view of a solar cell article according toan example of the present disclosure. This diagram is merely an example,and should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. A solar cell 100 is shown. The solarcell 100 has a substrate member having a surface region. The surfaceregion is an aperture region exposing photovoltaic material. In anexample, the photovoltaic material can be silicon, polycrystallinesilicon, single crystalline silicon, or other photovoltaic materials.

In an example, the cell 100 has the surface region comprising a spatialregion and a backside region. The cell has a first end strip 102comprising a first edge region 104 and a first interior region 106 asprovided on the spatial region. In an example, the first interior region106 comprises a first bus bar 108, while the first edge region on thespatial region has no bus bar. In an example, the first end strip has anoff cut 110 on each corner. Each of the off cuts 110 is about 45 degreesin angle, and has a flat edge abutting a pair of edges at ninety degreesfrom each other, as shown.

After the first bus bar 108, the solar cell has a plurality of stripsprovided on the spatial region. As shown, each of the strips 112 has abus bar 114 along an edge furthest away from the first bus bar 108. Eachof the strips 112 is substantially rectangular in shape, and can beconfigured with edges at ninety degrees from each other.

In an example, the cell 100 has a second end strip 116 comprising asecond edge region 118 and a second interior region 120. In an example,the second interior region 120 comprises a second bus bar 122 such thatthe second bus bar and the bus bar 114 from one of the plurality ofstrips forms a gap defining a scribe region 124. In an example, thesecond edge region 118 comprises no bus bar.

In an example, the first end strip 102, the plurality of strips 112, andthe second end strip 116 are arranged in parallel to each other andoccupy the spatial region such that the first end strip, the second endstrip, and the plurality of strips consists of a total number of five(5) strips.

In an example, the backside region 126 comprises the second end strip116 comprising the second edge region 118. In an example, the secondedge region 118 has a second backside bus bar 126 such that the secondbackside bus bar 126 and the second bus bar 122 are provided betweenphotovoltaic material of the second end strip. FIG. 2 is a front viewthereof. FIG. 3 is a back view thereof. FIG. 4 is a top view thereof.FIG. 5 is a bottom view thereof. FIG. 6 is a first side view thereof.FIG. 7 is a second side view thereof.

FIGS. 8-12 are illustrations of an edge photovoltaic strip 800 accordingto an example of the present invention.

FIGS. 13-17 are illustrations of a center photovoltaic strip 1300according to an example of the present invention.

FIGS. 18-20 illustrate a photovoltaic string 1800 according to anexample of the present invention.

FIGS. 21-25 illustrate a solar module 2100 according to an example ofthe present invention.

FIG. 26 is a front view of a solar cell 100 in an example of the presentinvention.

FIG. 27 is a side view of the solar cell 100, including bus bars, in anexample of the present invention. The solar cell 100 includes aphotovoltaic substrate 2704, a conductive backing material 2702, andmetallized surfaces 2706 and 2708.

FIG. 28 is an expanded view of a bus bar region of a solar cell 100 inan example of the present invention.

In an example, the present invention provides a method of manufacturinga solar module. The method includes providing a substrate member havinga surface region. In an example, the substrate is a solar cell 100 asdescribed in the present specification. The solar cell 100 is made ofphotovoltaic material, which has various features.

Features of FIG. 28 will be explained with respect to the numberingprovided in FIG. 1. In an example, the surface region comprises aspatial region and a backside region, a first end strip 102 comprising afirst edge region 104 and a first interior region 106 as provided on thespatial region. In an example, the first interior region 106 comprises afirst bus bar 108, while the first edge region 104 on the spatial regionhas no bus bar, and a plurality of strips 112 as provided on the spatialregion. In an example, each of the strips 112 has a bus bar 114 along anedge furthest away from the first bus bar 108, a second end strip 116comprising a second edge region 118 and a second interior region 120,the second interior region 120 comprising a second bus bar 122 such thatthe second bus bar 122 and the bus bar 114 from one of the plurality ofstrips 112 forms a gap defining a scribe region 124, the second edgeregion 118 comprising no bus bar, the first end strip 102, the pluralityof strips 112, and the second end strip 116 arranged in parallel to eachother and occupying the spatial region such that the first end strip102, the second end strip 116, and the plurality of strips 112 consistsof a total number of five (5) strips 112, the backside region comprisingthe second end strip 116 comprising the second edge region 118, thesecond edge region 118 having a second backside bus bar 126 such thatthe second backside bus bar 126 and the second bus bar 122 are providedbetween photovoltaic material of the second end strip 116.

In an example, the method includes separating each of the plurality ofstrips 114. The method includes separating the first end strip 102, andseparating the second end strip 116 by scribing via the scribe region124 and removing the second end strip 116. Each of the separationprocesses can occur along a spatial direction of the substrate.

In an example, the method includes transferring the first end strip 102in a first magazine, transferring each of the plurality of strips 114into a second magazine or a plurality of magazines, and transferring thesecond end strip 116 into a second magazine. In an example, the methodincludes selecting each of the plurality of strips 114, and arrangingthe plurality of strips in a string configuration. The method thenincludes using the string in a solar module.

In an example, the substrate member comprises a silicon material, thebackside region further comprising a first backside bus bar on the firstend strip, and a plurality of bus bars respectively formed on theplurality of strips.

In an example, the substrate member has a dimension of 156 mm and withinabout two mm, but can be others.

In an example, each of the strips has a desired width to be assembled inthe string configuration.

In an example, the plurality of strips are monolithically connected witheach other. In an example, each of the plurality of strips has anaperture region. Further details of the present invention can be foundthroughout the present specification and more particularly below.

FIGS. 29-33 illustrate a solar cell 100 under a cut and separationprocess according to an example of the present invention. FIGS. 29 and30 are isometric and front views that show a scribe region 2900 of asolar cell, including a kerf 2902 that is cut through a backing material2904 and a photovoltaic material 2906.

FIG. 31 shows a cell 3100 that has been subjected to a separationprocess. The separated cell 3100 includes a first edge strip 3102, asecond edge strip 3104, and three strips 3106 from middle portions ofthe cell. FIG. 32 shows a backside view of the separated cell 3100, andFIG. 34 shows an isometric view of the separated cell 3100.

FIG. 34 is a top view of a photovoltaic string 3400 according to anexample of the present invention.

FIG. 35 is a side view of the photovoltaic string 3400 according to anexample of the present invention focused on a cell to cell overlap inthe string. The photovoltaic string includes a plurality of strips 3500that are bonded together by an ECA layer 3502. Each strip comprises abacking material 3504, which may be a thickness of aluminum, and aphotovoltaic material 3506. The ECA 3502 is bonded between a conductivemetallized layer 3510, which may be a bus bar, that is disposed betweenthe backing material 3504 and the photovoltaic material 3506. Theexposed ends of the strips 3500 show a kerf 3512 and a fracture plane3514 from a scribing and singulation process.

FIG. 36 is a simplified diagram of a simplified system diagram accordingto an example of the present invention showing 24 strings coupledtogether in a single module.

In an example, the present method and system utilized a ⅕^(th) stripwidth versus ⅓^(rd), ¼^(th) or ⅙^(th) of a cell strip width based uponsome unexpected benefits and/or results, as shown in the table below.

PV Width Comment Width 78 52 39 31.2 26 mm Cell Current 4.5 3 2.25 1.81.5 Isc = 9A standard cell Fingers 80-200 80-150 80-120 80-100 80(Microns) Based on standard cell finger Shading 7.0% 5.8% 5.0% 4.5% 4%Finger shading Cell Utilization 98.7% 97.4% 96.2% 94.9% 93.6% 2 mmoverlap Placements 2X 3X 4X 5X 6X Over standard module Fill Factor 76%77% 78% 79% 79%

In the table, width refers to the width of a strip after it has been cutfrom a cell. Current is the amount of current that a strip produces,which is directly proportional to the size of the strip. Fingers carrycurrent across a strip, while shading is the area of the strip shadowedby the fingers. Cell utilization is the amount of area in a string inwhich strips do not overlap one another. The number of placements is howmany strips are cut from a cell and placed in a string. Fill factor isthe efficiency of the photovoltaic material present in a string comparedto its maximum power producing potential.

In an example, modules are configured to have current and resistancecharacteristics that are similar to a conventional module (Voc, Vmp,Isc, Imp, Power). However, modules can be designed to have differentcharacteristics for different applications. For example, modules createdaccording to embodiments of this disclosure can be configured to havelower voltage and higher current for the solar tracking applications,and to have higher voltage and lower current for residential modulesthat interface with module power electronics.

In an example, the present method and design uses a 31.2 mm strip width,which optimizes module characteristics, as well as providing a currentand voltage similar to standard modules. This allows embodiments to takeadvantage of standard inverters, electronics, and mechanical features.However, embodiments are not limited to these dimensions, and can beapplied to other sized strips as well.

FIG. 37 shows an embodiment of a process 3700 for scribing andsingulating a solar cell using laser energy, which will be explainedwith respect to FIG. 38, which illustrates a laser cutting system 3800.The laser cutting system 3800 includes a scanner 3802 that projects acutting laser beam 3804 that is focused by a lens 3806 to a laser spot3808, which corresponds to a focal point of the lens 3806. In someembodiments, one or more elements of the laser scanner may be referredto as a galvanometer. In an embodiment, the laser spot is from 18 to 30microns. In an example, the laser scanner 3802 receives laser energy3803 from a beam expander (not shown), which is reflected by a pluralityof mirrors from a laser source (not shown).

A cell 100 is located on a laser table 3810 at S3702. In one example,the laser table 3810 includes a vacuum chuck, or vacuum plate, which isdefined by a flat upper surface with a plurality of holes 3812 throughwhich a vacuum is applied. When the vacuum is applied, the negativepressure retains a face of the cell in place so that it is stationarywhen the exposed cell surface is scribed. In other embodiments, thelaser table 3810 may be outfitted with one or more clamp mechanism thatretains a solar cell 100, or retains a fixture to which a solar cell isaffixed. In an example, the cell 100 is mounted so that its backsidesurface, which may be a conductive metal surface such as aluminum, isoriented upwards towards the laser. A distance between the upper surfaceof the solar cell 100 and the lens 3806 may be between about 250 and 350mm.

A stream of air 3814 is initiated to flow across the surface of the cell100 at S3704. The air stream is delivered by an air source 3816 and isreceived by a vacuum port 3818 located on the opposite side of the cell100 from the air source 3816. In an embodiment, the air supplied throughthe air source 3816 is a laminar flow, as opposed to turbulent air, sothat the air stream 3814 picks up dust particles generated by the lasercutting process and directs those dust particles to the vacuum port3818, thereby effectively removing the dust particles from the chamber.Turbulent air flow carries the risk of redistributing dust particleswithin the laser system 3800, resulting in additional cleaning stepscompared to a system that uses laminar flow. In an example, the airstream 3814 is a focused air stream that is directed to pass directlyover a kerf as it is being cut.

The laser system 3800 may be outfitted with a distance sensor 3820. Inan example, the distance sensor 3820 emits a laser beam 3822 andmeasures a reflection from that beam to determine a thickness of thesolar cell 100. While solar cells 100 are manufactured to have a targetthickness, process variation results in a thickness tolerance that canaffect the depth of a laser kerf relative to the thickness of a cell.For example, solar cells that have a target thickness of 200 microns mayhave a tolerance of +20/−30 microns, so that the cells can range between170 and 220 microns in thickness. Accordingly, the distance sensordetermines the distance to the upper surface of cell 100, and using thedistance from the distance sensor to the top of the laser table 3810,the sensor can determine a thickness value for the cell at S3706.

When the thickness of the cell 100 is known, cutting parameters may bedetermined at S3706. The cutting parameters may include, for example, alocation of the spot 3808, or focal point of laser cutting beam 3804, inthe vertical dimension, a horizontal travel velocity, an energy level ofthe laser beam 3804, a laser pulse frequency, a number of passes acrossthe cell 100, etc. For example, a thicker cell 100 may be cut by usingadditional passes, a slower travel speed, and a different laser spotlocation, relative to a thinner cell. However, in other embodiments,predetermined parameters are entered into the laser system 3800.

The laser spot is passed across the exposed surface of a cell 100 atS3710 in a first pass. In various embodiments, the table may moverelative to a stationary laser, or the laser may move relative to astationary table.

As the laser moves across the surface of a cell, it cuts out a kerfhaving a specific width or depth. For example, as seen in FIG. 39, akerf such as first kerf 3902 or second kerf 3904 is cut from a cell 100.In an example, a kerf is cut to its final depth using a plurality ofpasses, such as from 2 to 40 passes, from 5 to 30, passes, or from 10 to25 passes. Accordingly, after the first pass, additional passes are cutat S3712.

The laser cutting parameters may be determined at S3708 to ensure that akerf is created with desirable characteristics. Substantialexperimentation has determined that optimal kerf characteristics includea kerf depth D1 that is about half the thickness of a solar cell depthD_(cell). In an example, the final depth D1 of a kerf is from 40% to 60%of the cell thickness Dm′. In an example, the kerf width is from 15% to40% of the kerf depth, or from 7% to 20% of the cell thickness D_(cell).

When kerf width and depth dimensions are wider than these conditions,such as in the case of second kerf 3904 having a width W2 that issubstantially wider than the width W1 of first kerf 3902, a subsequentsingulation process is affected. Here, a singulation process includesapplying mechanical stress to a cell 100 near the location of a kerf toinitiate a crack that separates the cell into two pieces. As seen inFIG. 39, when singulation is performed on a cell having characteristicsof first kerf 3902, the resulting crack 3906 is relatively smooth andeven, and is close to the location of the kerf in the width dimension.In contrast, when singulation is performed with a less desirable kerfsuch as kerf 3904, the crack 3908 created by the singulation process isrough and may travel farther from the kerf in the width dimension.

While the first kerf 3902 is representative of a kerf that results fromlower laser power such as laser power from 20 to 40 watts, while thesecond kerf 3904 is representative of a kerf that would result from ahigher laser power than the first kerf, such as a laser power from 40 to60 watts. For example, the width of the second kerf 3904 issubstantially larger than the width of the first kerf 3902. In addition,while the bottom of the second kerf 3904 is substantially flat, thebottom of first kerf 3902 is notched, or has a “V” shape.

The first kerf 3902 that results from laser cutting according to anembodiment of the present disclosure may have width and depthcharacteristics that can be expressed in both absolute and relativeterms. For example, W1 may be from about 15 microns to 35 microns inabsolute dimensions, or from 20 microns to 30 microns. In anotherexample, W1 is from about 15% to 35% of the kerf depth D1. The depth D1may be from 40% to 60% of the total depth D_(cell) of the solar cell100. In absolute terms, depth D1 may be from 65 microns to 132 microns.The precise kerf dimensions of a given embodiment may be determined withrespect to dimensions of a given solar cell 100.

After all desired kerfs have been cut into a solar cell 100, one or morestring element of the cell may be marked with the laser using anidentifier that can be used to identify the string at S3714. FIG. 40shows an embodiment of a strip 4000 that includes an identifier 4002.Also shown is a bus bar 4004. Information in the identifier may include,for example, a lot number, a date of manufacturing, an origin ordestination, an order number, a serial number, a part number, etc. Theidentifier 4002 may be a one-dimensional bar code as shown in FIG. 40,or a two-dimensional code as known in industry.

In some embodiments, one or more letters or numbers may be applied inaddition to, or as an alternative to, a one or two-dimensionalidentifier. The identifier 4002 may be cut into the exposed backsidesurface of one or more of the strips that are defined by the kerfs cutas described above while the solar cell is still retained by the vacuumof table 3810. The same laser apparatus may be used to createidentifiers as is used to cut the kerfs, with substantially lower power.

The cell is removed from the laser system 3800 at S3714, and issubjected to a singulation process at S3716.

Smooth cracks have lower surface area than rough cracks. The increasedsurface area has a negative affect the performance of a cell. Inaddition, the rougher crack 3908 has a higher degree of variation as itpropagates, so it has increased variation in the width dimension. Thearea of the crack that crosses semiconductor material in the widthdimension directly affects the amount of energy that can be captured bya cell. In addition, a kerf with the characteristics of first kerf 3902is less susceptible to chipping than second kerf 3904. For thesereasons, the kerf 3902 is desirable compared to kerfs with othercharacteristics.

In an example, the wavelength of the laser cutting beam 3804 is from 200to 600 nanometers. Lasers with higher wavelengths, such as red orinfra-red wavelengths, tend to vaporize cell materials and create slag.While lower wavelength lasers such as UV wavelength lasers have highprecision, and can create a relatively narrow kerf width, they aregenerally more expensive and prone to failure. Accordingly, in anexample, the laser wavelength is in the green spectrum from 495 to 570nanometers. In other examples, the laser wavelength is from 520 to 550nanometers, from 525 to 540 nanometers, from 530 to 535 nanometers, andabout 532 nanometers.

Intuition suggests that throughput can be increased by raising the powerlevels, since higher power lasers general remove more material at afaster rate. However, after considerable experimentation, it has beendetermined that optimum laser cutting conditions occur at relatively lowpower levels. One reason for this is that higher power levels tend tomelt and vaporize solar cell materials. When solar cell materials aremelted, more energy is absorbed by the solar cell material, and slag iscreated, resulting in a relatively rough kerf.

In contrast, as seen in the experimental data shown in FIG. 41, lowerpower levels effectively remove material at a faster rate. One reasonfor this is that lower power levels cause an ablation mechanism in whichsmall particles, which can be described as dust particles, areeffectively chipped away from the cell material by the laser. Theexperimental data suggests that ablation uses less energy to remove avolume of solar cell material than melting and vaporization, which occurat higher power levels. In addition, lower power levels tend to resultin narrower kerf widths compared to higher power levels. Therefore, inan example, the laser energy when cutting a kerf in a solar cell 100 isfrom 20 to 35 watts.

The velocity of a cell 100 relative to a laser spot 3808 also influencesthe depth, width and roughness of a kerf. Higher velocities result inshallower cutting depths, which requires additional passes. In anexample process, the velocity of the laser relative to the cell is from4800 to 5000 mm/second, and from 2 to 40 passes are performed for eachkerf location. In other examples, the number of passes is from 5 to 30,and from 10 to 25. Experimental data showing relationships between cellvelocity and kerf depth at various frequencies is provided in FIG. 42.

In an embodiment, pulse energy may be from 100 to 500 microjoules perpulse, and pulse frequency may be from 100 to 400 kHz.

In an example, the present invention provides a method of separating aphotovoltaic strip from a solar cell. The method includes providing asolar cell comprising either a single crystalline silicon material or apolycrystalline solar cell, the solar cell having a backside and a frontside and a thickness, the backside having a metal material, and placingthe front side of the solar cell on a platen such that the backside isfacing a laser source. The method includes initiating a laser source tooutput a laser beam having a green wavelength and a spot size of 18 to30 microns and subjecting a portion of the backside to the laser beam ina reduced power level ranging from about 20 Watts to about 35 Watts tocause an ablation to form a scribe region having a depth, width, and alength, the depth being about ½ of the thickness of the solar cell, thewidth being about ¼ of the depth, and the length being equivalent to alength of the solar cell. The method includes detecting a thickness ofthe solar cell and adjusting a speed of a movement of the laser beambased upon a thickness variation of the thickness of the solar cell. Themethod includes repeating the step of subjecting to create a pluralityof scribe regions spatially disposed on the backside of the solarmodule.

In an example, the method includes moving the laser beam at a rate of4800 to 5000 mm per second. In an example, the method includessubjecting occurs at least twice along the scribe region. In an example,the scribe region is shaped as a notch as viewed along an end of thescribe region. In an example, the detecting comprises applying a redlaser to a surface solar cell to identify a height of the thickness ofmaterial. In an example, the adjusting comprises adjusting a number ofpasses for the scribe region to accommodate a thickness variation of thethickness of the solar cell. In an example, the detecting occurs using alaser having a different color than the laser beam from the lasersource. In an example, the method of separating occurs within a timeframe of 1 second to about 6 seconds to provide the plurality of scriberegions. In an example, the method further includes maintaining vacuumnear a vicinity of the solar cell during the subjecting. In an example,the method includes subjecting a jet of fluid within a vicinity of theablation to carry away particulate material, and capturing theparticulate material using a vacuum. In an example, the method includessubjecting a fluid, using a laminar flow, within a vicinity of theablation to carry away particulate material, and capturing theparticulate material using a vacuum. In an example, the method includesmaintaining the solar cell under a vacuum chuck to maintain the cell ina substantially flat position. In an example, the scribe region is astraight line +/−10 microns. In an example, the method includes scribinga unique identifier on each of the strips.

Exhibit 1, which is hereby incorporated by reference, is attached.

While the above is a complete description of specific embodiments of theinvention, the above description should not be taken as limiting thescope of the invention as defined by the claims.

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art and areto be included within the spirit and purview of this application andscope of the appended claims.

The invention claimed is:
 1. An apparatus comprising: a solar modulehaving a plurality of strings, each of the plurality of strings beingconfigured in a parallel electrical arrangement with each other; aplurality of overlapped photovoltaic strips forming each of theplurality of photovoltaic strings separated from a solar cell, an edgeof each of the overlapped photovoltaic strips comprising, a kerf in aback side of the strip having a depth of from 40% to 60% of a thicknessof the solar cell and cut by an ablation from multiple passes of a laserbeam, and a crack extending from the kerf to a front side of thephotovoltaic strip, the crack initiated by application of stress; afirst end termination configured along a first end of each of theplurality of strings; and a second end termination configured along asecond end of each of the plurality of strings.
 2. The apparatus ofclaim 1 wherein the crack defines a fracture plane.
 3. The apparatus ofclaim 1 wherein the thickness is from 170 to 220 microns.
 4. Theapparatus of claim 1 wherein the depth is between about 65 and 132microns.
 5. The apparatus of claim 1 wherein each of the plurality ofoverlapped photovoltaic strips comprises a plurality of fingers on thefront side.
 6. The apparatus of claim 5 wherein the plurality of fingersis between about 80-200 fingers.
 7. The apparatus of claim 5 wherein theplurality of figures impose a shading of between about 4-4.5%.
 8. Theapparatus of claim 1 wherein each of the plurality of overlappedphotovoltaic strips comprises a bus bar on the front side.
 9. Theapparatus of claim 1 wherein each of the plurality of overlappedphotovoltaic strips comprises a bus bar on the back side.
 10. Theapparatus of claim 1 wherein each of the plurality of overlapped stripscomprises an off cut corner.
 11. The apparatus of claim 1 furthercomprising an Electrically Conducting Adhesive (ECA) between overlappedphotovoltaic strips.
 12. The apparatus of claim 1 wherein the pluralityof overlapped photovoltaic strips have an overlap distance of about 2mm.
 13. The apparatus of claim 1 wherein each of the plurality ofoverlapped photovoltaic strips has a width of about ⅕^(th) a width ofthe solar cell.
 14. The apparatus of claim 13 wherein each of theplurality of overlapped photovoltaic strips has the width of about 31.2mm.
 15. The apparatus of claim 1 wherein each of the plurality ofoverlapped photovoltaic strips has a width of about ⅙^(th) a width ofthe solar cell.
 16. The apparatus of claim 15 wherein each of theplurality of overlapped photovoltaic strips has the width of about 26mm.
 17. The apparatus of claim 1 wherein the crack is formed by theapplication of mechanical stress.
 18. The apparatus of claim 1 whereinthe laser beam has a wavelength in an ultraviolet (UV) portion of thespectrum.
 19. The apparatus of claim 1 wherein the laser beam comprisesan infrared (IR) laser.
 20. The apparatus of claim 1 wherein themultiple passes of the laser beam comprise a repetition rate of betweenabout 100-300 kHz.